DOC: Add outlines documentation and link it in User Guide

[mainuddin-md]

This adds documentation for reading and adding PDF outlines/bookmarks
as requested in issue #3484. Linked in User Guide.

[stefan6419846]

Thanks for the PR.

• Please have a look at the failing tests.
• Please move user docs to the user-specific directory.

[mainuddin-md]

Hi @stefan6419846 ,

I have resolved the failing tests and moved the user docs to the user-specific directory.

Please review.

[stefan6419846]

Could you please align this new guide with the other ones which have changed to execute the actual example code in the meantime?

[mainuddin-md]

Hi @stefan6419846,

Thanks for the feedback, I’ll align the new guide with the other ones that execute the actual example code and update the PR soon.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.16%. Comparing base (310e571) to head (fa6c927).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3511   +/-   ##
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  Coverage   97.16%   97.16%           
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  Files          57       57           
  Lines        9809     9809           
  Branches     1781     1781           
=======================================
  Hits         9531     9531           
  Misses        167      167           
  Partials      111      111           

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[mainuddin-md]

I have modified the PR to execute the actual code examples. Please review.

[stefan6419846]

Thanks for the update. Judging from the structure etc., it seems like this is mostly auto-generated using AI - which is no issue as long as you have checked the changes yourself and it follows our usual structure.

Unfortunately, I cannot merge this as-is:

• Could we please use subsections instead of separate files for reading and writing?
• Why is the introduction a note in one case, but regular text in the other. I guess we should make this regular text.
• The user docs are not for resembling the exact API and describing the parameters. These should go into the docstrings. If required, link to the corresponding methods/classes in your description using the corresponding Sphinx directive/role.
• Please do not save arbitrary (and large) files in the resources directory. If you keep the order "Add" - "Read", you should be able to re-use the generated file in the second examples.
• Do not import from internal modules like _fit. Use the public API only!
• Instead of creating a reader and writer and adding the pages manually, just use writer = PdfWriter(clone_from="input.pdf").
• The description of what the code does usually goes before it. This should be no list, but a short descriptive text.
• If you decide to include screenshots, please make sure that they ideally resemble the input document and you have the necessary rights to include it. If highlighting is required, use proper drawing tools to get nice rectangles instead of arbitrary drawings.

Please note that I might have missed some aspects during this review due to merging this requires some larger changes anyway.